Sheet guiding devices are provided at various locations within a printing machine including, for example, in the deliverer and in the transfer system between the printing units in order to guide the sheets of printed material as they are conveyed through the printing machine. One example of such a guiding device is disclosed in DE 28 46 643 Al. The sheet guiding device disclosed in this reference is arranged in the sheet deliverer of a printing machine and comprises sheet guiding brackets which are adjustably mounted across the width of the printing machine and pivotable suction boxes that are arranged between the sheet guiding brackets.
A sheet-guiding device which has guide surfaces having a plurality of openings therein is disclosed in EP 0 156 173 Bl. The guide surfaces have associated flow ducts which are in fluid communication with fans that are selectively operable to provide either a positive air flow or a negative or suction air flow through the openings in the guide surfaces.
Another sheet guiding device is disclosed in DE 43 08 276 Al. This particular sheet-guide device also has a plurality of openings through which air can be blown. One of the openings is formed by a front face integrated into the sheet guide surface as an impact surface and includes a flow duct which opens at an angle into the into the sheet guide surface.
One of the significant problems associated with the pneumatic sheet guiding systems used in these and other prior art designs is that they take very little account of the format of the printed material being processed in a particular print run. Specifically, when the printed material being processed has a format different from the maximum which can be handled by the printing machine, the operation of the pneumatic guide system can cause air flow disturbances which can lead to sheet flutter. Accordingly, these sheet guiding systems do not guide printed materials having different formats in a uniform manner. These air flow disturbances can result from effective air flow losses which occur as a result of processing printed material which has a format less than the maximum which can be processed by the printing machine. One method which can be used to compensate for these air flow disturbances is to increase the volume of air flow provided by the air system powering the pneumatic guide system. However, this results in an increased power consumption and, in turn, increased manufacturing costs.